The invention relates generally to membrane structures. More particularly, the invention relates to membrane structures having substantially high flux and substantially high selectivity. The invention also relates to a method of manufacturing membrane structures, on an industrial scale.
Porous membrane structures are extensively used in filtration, separation, catalysis, detection, and sensor applications. Membrane structures with extremely fine pore sizes may be required for biofiltration and bioseparation applications. The selectivity of a membrane is typically determined by the membrane pore size—high selectivity membranes have small pores. However for a given thickness, the smaller the pore size, the smaller the membrane flux. Therefore, membrane layers with fine pores must be made thin to ensure sufficient permeate flux. Typically thin membranes with small pores are stacked on thicker substrates with coarser pores, which provide mechanical support but do not significantly increase the resistance to flow. In such membrane structures, it is extremely difficult to get a defect-free, interface between layers to ensure sufficient connectivity through the membrane structure. In spite of much effort, there is a demand for membrane structures with fine pores exhibiting substantially high permeance and high selectivity, along with methods to produce, on an industrial scale, such membrane structures.